This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Nemean Lion (Greek)
The Nemean lion was a monster in Greek mythology that lived at Nemea. Eventually, it was killed by Heracles (Hercules). Because its golden fur was impervious to attack, it could not be killed with mortals' weapons. Its claws were sharper than mortals' swords and could destroy any strong armour.
In Bibliotheca, Photius wrote that the dragon Ladon, who guarded the golden apples, was his brother. Heracles wore the Nemean lion's coat after killing it, as it was impervious to the elements and all but the most powerful weapons. Others say that Heracles' armour was, in fact, the hide of the Lion of Cithaeron.